New energy vehicles are widely promoted in the country and even in the world. However, in order to completely replace fuel vehicles, there are many areas for improvement. For example, there are a few problems such as low travelling mileages of vehicles, high cost of battery packs, reliability of battery packs and the like, which need to be further solved. In view of these problems, higher requirements have been proposed for a power battery as a core part of an electric vehicle, such as higher energy density, lower cost and so on.
Currently, the power battery generally has a quadrate hard-shell structure. Housing of the power battery includes a shell and a cap assembly. The housing of the power battery provides a sealed space to accommodate an electrode assembly and electrolyte. The power of the electrode assembly is directed to outside of the sealed space from inside of the sealed space through a terminal of the cap assembly. In the existing cap assembly, cap plate is a metal plate and a through hole is disposed thereon. The terminal is divided into a base portion and an extension portion, and the base portion has a cross-sectional area larger than that of the through hole. During assembly, the base portion is located below the cap plate (i.e., inside the shell). After the extension portion passes through the through hole, the extension portion is fixed by a snap spring or a rivet connection. In this way, the terminal is fixed to the cap plate. As the base portion is located inside the shell, space utilization within the shell is reduced, and as a result, the energy density of the power battery is reduced. Moreover, as it is required to provide the terminal with a base portion and a long extension portion, the terminal may not be directly press-molded, and instead, the terminal is required to be molded individually by a respective machine, so that manufacturing cost of the terminal increases.
In addition, the base portion inside the shell is provided with a certain thickness, usually 1.5 to 4 mm, in order to connect the terminal to the wiring board inside the battery shell, thus the space utilization in the battery shell is reduced and the manufacturing cost is increased.
Therefore, there is a need for a new secondary battery and a new battery module.